In the related art, an electronic control unit (ECU) which controls an operation of a vehicle is provided with a driver integrated circuit (IC) which drives a vehicle load, and a microcomputer which controls the drive IC, and drives and controls the vehicle load by transmitting a parallel signal from a microcomputer to the driver IC.
Meanwhile, in recent years, the level of functions required in the ECU and a demand for low costs have increased. Here, in order to reduce the cost by reducing the number of ports of the microcomputer, it has been attempted to switch the parallel signal which is transmitted and received between the microcomputer and the driver IC to a serial signal. Communication in accordance with a micro-serial bus standard is an example thereof.
When the microcomputer and the driver IC communicate with each other by the serial signal, a plurality of control commands send and receive serial data which is written in series. In this case, when an abnormality occurs in the serial communication between the microcomputer and the driver IC, a control command with respect to the entire vehicle load driven by the driver IC becomes abnormal. Therefore, when an abnormality occurs in the serial communication between the microcomputer and the driver IC, it is considered that immediate detection of the abnormality and a shift of the vehicle into a fail-safe mode are necessary.
In the following PTL 1, a technology which relates to the detection of an abnormality of an electronic control unit, and detects an abnormality by echoing back (sending the data which is the same as the data received by a receiving side back to a transmitting side) control data, is described.
In the following PTL 2, a technique which relates to detection of an abnormality of an electronic control unit, and in which a detection signal is transmitted from a comparator 23 to a transceiver 12, the comparator 23 receives a comparison signal from the transceiver 12, and both the signals are compared to each other and the result thereof is reported to a CPU 21, is described. In PTL 2, by using the technique, it is detected whether or not there is a location where a signal line between a microcomputer 11 and a transceiver 12 is disconnected.
In PTL 3, it is described that, in communication between a main computer 1a provided in an ECU1 and a sub-computer 1b, the sub-computer 1b transmits data which is read out when a reading mode is performed and data in which all of the bits of the read-out data are inverted to the main computer 1a, and the main computer 1a compares the data to each other. The main computer 1a confirms whether or not the read-out data which is received from the sub-computer 1b is normal, by the above-described processing.